With increasing use of home video recorders/players (referred to hereinafter as VCRs) there is an increasing need to determine whether a video signal is from a VCR or is a broadcast signal. It is desirable to provide a display on a television receiver to indicate to the viewer whether he is watching a VCR playback or a broadcast program, and the television itself may advantageously use such information. For example, an identifier signal indicating the type of video signal would enable other circuitry in the television to select the best method for achieving synchronization with the video signal. Also, such identifier signal would be useful in controlling a pay T.V. system.
With the increasing need to determine the type of video signal sources, there arises an increased need for an accurate and reliable method for making this determination. Reliability in producing an identifier signal is hampered by the wide quality range of signals produced by VCRs and by the wide range of signal-to-noise ratios found in T.V. broadcast signals. Thus, a heed exists for a circuit that will reliably identify a VCR signal and a T.V. broadcast signal despite the difficulties posed by the expected operating conditions.